1. Field of the Invention
The present invention relates to a magnetic head having a structure of CPP (Current perpendicular to the plane), which allows a sense current to flow perpendicular to a stacking plane of magnetoresistive films, and a magnetic disk drive on which the magnetic head above is mounted.
2. Discussion of the Background
Recently, recording density of a magnetic disk drive is made higher at a phenomenal rate, such as at an annual growth rate of 100%. With such enhancement in recording density, a high output magnetic head is required to be mounted on the magnetic disk drive.
In order to achieve such a high output magnetic head, performance of a magnetoresistive film is being enhanced. Up to the recording density of around 3×108 bits per 1 cm2, an anisotropic magnetoresistive (AMR) film has been used. However, for a recording density equal to or higher than the value above, a giant magnetoresistive (GMR) film was developed and it has been improved until now. Even with the giant magnetoresistive film, there is a concern that the output may be insufficient for the recording density higher than 9.3×109 bits per 1 cm2. Therefore, following films have been researched and developed as a next-generation magnetoresistive film subsequent to the GMR film: Tunneling magnetoresistive (TMR) film as described in “Journal of Magnetism and Magnetic Materials”, issued in 1995, vol. 139, pp. L231 to L234, and CPP (Current perpendicular to plane)-GMR film, which allows a current to flow perpendicular to a stacking plane of GMR films, as described in “Journal of Applied Physics”, issued in 2001, vol. 89, pp. 6943 to 6945.
Here, it is to be noted that there is a large difference in structure between the magnetic head which employs AMR film or GMR film, and the magnetic head which employs TMR film or CPP-GMR film. The former has a structure of CIP (Current into the plane) to allow a sense current to pass through into the in-plane direction of the plane of the magnetoresistive film comprising AMR film or GMR film, and leads for supplying the sense current are provided on both sides of the magnetoresistive film. On the other hand, the latter has a structure of CPP (Current perpendicular to the plane), which allows the sense current to flow approximately in perpendicular direction with respect to the film surface of the magnetoresistive film comprising TMR film or CPP-GMR film. With this structure, the leads are required to be provided in stacked manner on the magnetoresistive film. Accordingly, as to the leads and a lead line for leading the sense current to the leads, it is necessary to contrive a new structure, which is different from the magnetic head of CIP structure.
Regarding a structure of the leads and the lead line in the CPP structure, Japanese Patent Application Laid-open No. 2001-67628 discloses that an entire upper lead layer exists extendedly within an area where a lower lead layer is formed in a plane view. Japanese Patent Application Laid-open No. 2002-25016 discloses a structure where the lead line electrically connected with the upper shield layer is patterned so that an area of the lead line located above the lower shield layer becomes small.